# - A - B - C - D - E - F - G - H - I - J - K - L - M - N
O- P - Q - R - S - T - U - V - W - X - Y - Z
RADIUS (REMOTE ACCESS DIAL-IN USER SERVICE)
A server for authentication, authorization and accounting (AAA) of endpoints and endpoint aliases.
RAS (REGISTRATION, ADMISSION & STATUS)
In an H.323 audio or video system, the RAS protocol is a control channel over which H.225.0 signaling messages are sent.
REAL-TIME
The processing of information that returns a result so rapidly that the interaction appears to be instantaneous. Video conferencing is an example of a real-time communication application.
REDUNDANCY
Duplicating equipment components to achieve high availability of telcom equipment and service continuity.
REGISTERED ENDPOINT
A registered endpoint is an endpoint that has informed the Gatekeeper that it is online, active and ready to receive calls, and has received confirmation from the Gatekeeper of its registration request.
RESOLUTION (Display Resolution)
Resolution, or Display Resolution, typically refers to the size of the displayed image in distinct pixels in each dimension that can is displayable.
In video coding it refers to the pixel dimensions of the coded images. For instance, 720p resolution is 720x1280 pixels.
Resolution can also be either Interlaced or Progressive. In interlace resolutions the video stream is actually comprised of two sequential streams at double the frame rate, one with the odd numbered lines and the other with even numbered lines. In progressive resolution the video stream holds complete frames. 1080p will therefore mark a 1080x1920 resolution that is progressive, 1080i will mark a 1080x1920 resolution that is interlaced.
Other examples of common resolutions are:
qCIF 176x144
CIF 352x288
4CIF 704x576
480p 480x848
352p 352x624
ROAMING
The ability for a user to function in a serving network different from the home network. The serving network could be a shared network operated by two or more network operators.
ROUTED MODE
The routing of the Call Setup channel (Q.931) and the Control channel (H.245) through the Gatekeeper.
See also Q.931 + H.245 Routed Mode
ROUTER
A device or setup that finds the best route between any two networks, even if there are several networks to traverse. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs.
RTP/RTCP (REAL TIME TRANSPORT PROTOCOL / REAL TIME CONTROL PROTOCOL)
Real Time Transport Protocol / Real Time Control Protocol - RTP is an IP protocol that supports real-time transmission of voice and video. It is widely used for IP telephony. RTCP is a companion protocol that is used to maintain QoS.
RTP REDUNDANCY
A method of overcoming packet loss by doubling packet payload without increasing the number of packets sent.
See also FEC
RTSP (REAL TIME STREAMING PROTOCOL)
A protocol for use in streaming media systems which allows a client to remotely control a streaming media server.